Problem: Tiffany has taken 3 tests and her average score so far is 80. If she gets 100, a perfect score, on the remaining 2 tests, what will her new average be?
Explanation: If she gets 100 on the remaining tests, the sum of her scores will be $3 \cdot 80 + 2 \cdot 100 = 440$ Her overall average will then be $440 \div 5 = 88$.